Wastewater System

The City's wastewater system provides service to Greenfield and the surrounding unincorporated areas. Wastewater services include the transmission of wastewater from residential, commercial, and light industry areas to a treatment facility and the disposal of the wastewater and residual waste solids. The City's authority to discharge wastewater is granted under a Waste Discharge Permit issued by the Central Coast Regional Water Quality Control Board. The City's existing permit was issued in May of 2002 and it increased the City's allowable discharge to 1.5 million gallons per day (MGD) from the previous limit of 1.0 MGD.

The sewer plant operates at a flow of approximately 930,000 gallons per day (GPD) and has approval to expand the plant to a capacity of 2.0 MGD. The treated water is not stored, but is dispersed using spray fields. The wastewater system includes over 110,000 feet of gravity sewer ranging in diameter from 6 to 24 inches. The City has over 3,200 sewer connections.
A large grey tank that holds waste water.

Connection Types


The overwhelming majority of the City's sewer connections are for single family residential (SFR) accounts. SFR accounts make up 83% of the service connections; multi-family customers make up approximately 11%; commercial make up 4%; landscapes make up 1 %; and 1% are fire protection, government and hydrant use, water and residual waste solids. It's under the City's authority to discharge wastewater.

The City does not charge for sewer service based on sewer flow or distinguish between the differing wastewater characteristics of different customer types who discharge into the wastewater system. This rate schedule is based on the recommendation of a previous rate study that concluded that determining a customer's sewer flow per connection is difficult due to variations in the type of land use, irrigation needs and time of year.

Wastewater Treatment Plant


The City's Secondary Wastewater Treatment Plant (WWTP) is part of the Wastewater Division and is presently regulated by the California Regional Water Quality Control Board, Central Coast Region, and Waste Discharge Requirements (WDR) Order Number R3-2002-0062. The Order was adopted May 31, 2002, for operating at 1 Million Gallons Per Day (MGD). Presently, staff is moving forward to expand the plant to 2 MGD capacity in order to handle present and anticipated future flows.

Basically, there are 2 components for treating the City's raw wastewater at the plant. The first is collecting, sterilizing and disposal of the bio-solids better known as sludge; the second is cleaning the liquid portion known as effluent, and dispersing the effluent through a gravity flow irrigation system onto a 24 acre field for ground percolation. The process to clean effluent is known as Secondary Treatment. Additionally, operation and maintenance includes daily testing and monitoring of in-fluent and effluent including sludge processing and disposal to comply with strict State regulations at the plant.
A waste water pond filled with water with a platform over it.

Collection System


The Sewer Collection System is part of the City's Wastewater Division and is responsible for performing the operation and maintenance of the City's 21 mile of gravity sewer collection pipelines, force mains, and 6 lift stations. The Division adheres to the City adopted Sewer System Management Plan (SSMP) for operation and maintenance and includes preparing and implementing an overflow emergency response plan; a fats, oils and grease control program (FOG); a system evaluation and capacity assurance modifications program; and a monitoring and measuring program.

The SSMP is required by the State Water Resources Control Board in compliance with adopted Water Quality Order Number 2006-0003 established by the Statewide General Waste Discharge Requirements. Additionally, the Division will be logging pertinent maintenance and operations information of the City's new Geographical Information System (GIS) Program.

The fiscal year 2016 budget includes $12,000 for lift station pumps and a root cutting kit, $150,000 for a back-up generator and $30,000 for a trailer trash pump. Equipment purchases for implementing the System Evaluation and Capacity Assurance Modifications Program have been deferred until the completion of the sewer master plan and revenue sufficiency study.